Projectors are great in any home theatre but can be a nuisance if you just need to quickly set a recording on the PVR or to just stream music. That's where a second screen comes in handy that slides away when not in use.
Inspired by videos of television’s rising from the foot of the bed, and with a little ingenuity, Steven set up a screen that would lift from behind the HiFi cabinet so he could set his PVR. We spoke to him to learn more about the setup.
WARNING: Steven’s project involves working with 240V mains power. In Australia, a person cannot legally work on voltages above 50Vac without a licence. Any mains wiring is very dangerous for those not qualified and experienced with it. This circuit could easily be adapted to switch the DC-side of any power supplies, which is how we recommend this idea should be adapted. DIYODE cannot take any responsibility for harm caused by anyone dealing with mains power, and we do not recommend replication of this circuit as published.
Steven's Build:
Steven has kindly supplied us with a parts list, fritzing diagram and code to be able to construct a similar project of your own (however please note the warning above). The code can be downloaded from the digital resources for this article.
| Parts Required: | Jaycar | Altronics | Core Electronics |
|---|---|---|---|
| 1 × LeoStick | - | - | CE04489 |
| 1 × 4 Channel Relay Driver Module | - | - | CE04548 |
| 1 × 10k Resistor* | RR0596* | R7582* | PRT-14491 |
| 1 × 15k Resistor* | RR0600* | R7586* | - |
| 1 × 2.5mm Mono Plug | PP0100 | P0020 | - |
| 1 × Momentary Action Push Button | SP0700 | S1084 | COM-11996 |
| 1 × 5V Solid State Relay | SY4088 | S4410 | - |
You’ll also need a Linear Motor (Steve used a S200-450-12-50), Power Supply and Driver Board. * Quantity shown, may be sold in packs.
Your pop-up screen is a great idea when you don’t need the projector. What convinced you to start this project?
Two reasons, one was that I often wanted to update the timer schedule on my PVR quickly and easily, and the other was as a screen for my music player. So I could select playlists and view album covers. At the time, small LCD HDMI screens were very expensive, and I had an old computer screen not being used. You also have to admit it’s a pretty cool talking point to show off. I think I’d also seen a bed somewhere, that had the TV come out of the foot of the bed. That gave me the idea that I could do the same.
That’s a handy solution to avoid firing up the projector each time. You have mounted the monitor to a linear actuator. Can you tell us more about the actuator and does it require persistent power to stop it from naturally winding back down?
I think the actuator was originally designed to move satellite dishes or solar panels to keep them pointing in the right direction. It uses a worm drive that is gear driven via a 12v DC motor. So depending on which way the DC power is applied, it changes which direction the actuator travels. It also includes internal limit switches with bypass diodes, so the power to the motor is automatically cut when the limit is reached (but only in one direction, allowing it to reverse). It runs from a 12v 5Amp power supply and controller. The controller has Open and Close inputs, alongside the 12V input, and contains 2 relays and fuses. One for power, and the second to reverse the polarity to the drive motor.
The tricky thing with the actuator, is the travelling end has to be held so that it cannot turn (due to the worm drive action). But the nice thing I found, was that its external dimensions of its case made it fit perfectly inside a 50mm square Fence post from Bunnings. So I cut a 150mm base to mount on a board for the stand, then used a thru bolt on end of the actuator, through the post and monitor mounting bracket. Thus the post slides up and down over the actuator case stopping it from turning.
It sounds like you are quite resourceful. We noticed in the “down” position you automatically cut power to the monitor. How have you achieved this?
I decided I wanted minimal power drain when not in use, so I added a relay to switch 240V mains supply. This mains supply was then used to power both the Monitor and Linear Actuator power supplies. Thus the only power drain when not being used, is the power for the Leostick, which comes from a USB port on my Power board.
Avoiding unnecessary power drain is a good thing to consider in any project to keep the power bill down. Can you tell us what the Leostick monitors in the receiver to activate up / down modes?
Most Surround Sound Receivers have what are called Trigger Outputs. These are normally used to power up external Power Amplifiers or other equipment. Unfortunately this is a very low power output (12V @ 20ma if you’re lucky) so can’t be used to power relays or anything else directly, but easily used as a level trigger.
WARNING: Steven’s project involves working with 240V mains power. In Australia, a person cannot legally work on voltages above 50Vac without a licence. Any mains wiring is very dangerous for those not qualified and experienced with it. This circuit could easily be adapted to switch the DC-side of any power supplies, which is how we recommend this idea should be adapted. DIYODE cannot take any responsibility for harm caused by anyone dealing with mains power, and we do not recommend replication of this circuit as published.
With my Amp, I can also configure each Amp Source separately, and choose which Trigger Outputs are turned on or off for each source. So I have two different Sources for the PVR, one with and one without the trigger set.
Using the trigger output from the amplifier is a clever solution. What else have you achieved with this build that might not be immediately apparent?
One of the quirks of my Receiver (and most) is that when it is powered on, it restores the last input used. Thus if I last used the Monitor, then next time I powered up, it would turn on the trigger, but then turn it off again when I switched inputs. To stop this happening, I added a minimum on time for the trigger input, thus it had to be on for a minimum length of time to be counted as the reason to turn on the power and raise the monitor, giving time for my Harmony Remote to power on the amp and switch inputs, before the monitor was raised.
Secondly, I added a manual switch to turn on or off the monitor and raise it. The software was written so the trigger is ignored, if the button was used to turn on the monitor. Thus I could use any source of the amp, and or configure the amp, without the monitor turning on and off.
It’s always handy when we have software to make simple adjustments to make things work better. If you started from scratch, would you change the approach, or was it about as successful as you wanted it to be?
As mentioned, the trigger works great, but I had to add the start delay in case I didn’t really want the monitor. I had changed to a different brand of Receiver, and it could turn the trigger on and off via the remote, so this delay wouldn’t be necessary. I would also think about attempting to build it internally in the power board. In this way the relay that switches 240V, could also be used to power any other stereo components, so these wouldn’t need to be in standby mode either. I could probably also build it with all 5v relays directly from the Leostick and not need the separate Linear Motor Controller or the 4 Channel Relay driver boards.
A NOTE FROM THE EDITOR: Isolation MUST comply with strict and arduous Australian Standards to avoid risk of electrocution and fire.
It would also be good to find a quieter linear motor, mine is a bit noisy.
You have done well to work with the devices you already owned without any additional expense. What is the biggest thing you’ve learnt, having developed your project?
Probably the biggest issues were around doing things in the right sequence and the timing involved.
Planning ahead is usually a great thing, but sometimes it can be difficult to foresee some things until you’re underway. Are you working on any amazing new projects?
I have way too many on the go. I’m trying to get a Bluetooth Proximity detector working for my garage roller doors. So when I turn up on my Vespa, the door simply opens, then closes when I switch off. A Raspberry Pi based sprinkler controller. A new prototyping controller called on obnix. I also tinker with my Raspberry Pi Home Automation controller, Weather station and many Sonoff based home automation gadgets.
Wow! That’s a lot to keep you out of trouble. Thank you for taking the time to tell us about your screen lift. We look forward to seeing your next completed project.